CROSS REFERENCE TO RELATED APPLICATION
This application is related to U.S. application Ser. No. 07/928,448, filed Aug. 12, 1992 now U.S. Pat. No. 5,355,432.
1. Field of the Invention
The present invention relates to a pattern matching method and pattern recognition apparatus to be preferably used for recognizing speech and image data.
2. Description of the Related Art
With conventional speech recognition apparatus, for example, an input speech (or an input pattern) is recognized by identifying a category of a word (or a standard pattern) to which the input speech belongs.
However, it should be noted that, even if a same word is spoken by a same speaker, a pattern of the word is not necessarily the same as that of the word spoken again by the same speaker, indicating that the category has an area more or less extending into a recognition space. For recognizing the category extended into the recognition space, a multi-template method is known, for example, in which a plurality of standard patterns are prepared for a single word.
With the conventional multi-template method, distances between an input pattern and templates (or standard patterns) are all calculated on a same distance scale, and one of the templates (or standard patterns) that is found minimizing a distance from the input pattern is regarded as a recognition result. Thus, performing pattern recognition on all templates by using the same distance scale is to determine whether a point representing an input pattern is contained in or touching one of circles (or spheres) of a same radius around a point representing a template (or a standard pattern) on a parameter plane. Therefore, enclosing neither too much nor too little, i.e., as accurately as possible, each of word categories shown in FIG. 7, for example, with circles (or spheres) having the same radius enhances recognition performance.